A wide variety of coatings have been used to coat the surfaces of food and beverage packages. For example, metal cans are sometimes coated using coil coating or sheet coating operations; that is, a plane or coil or sheet of a suitable substrate, for example, steel or aluminum is coated with a suitable composition and cured. The coated substrate is then formed into the can body or can end. Alternatively, the coating composition may be applied, for example, by spraying, dipping and roll coating, to the formed can and then cured. Coatings for food and beverage packages may be capable of high speed application to the substrate and provide the necessary properties when cured to perform in a demanding end use. For example, the coating should be safe for food contact and have acceptable adhesion to the substrate.
Coatings for food and beverage packages may contain external curing agents that are reactive with hydroxyl and/or carboxylic acid groups in the resinous binder. The curing agent can be a phenol-formaldehyde or an amine such as melamine, benzoguanamine or urea-formaldehyde condensate. Such curing agents, however, may be made with and/or release formaldehyde during the curing or crosslinking reaction. Minimizing if not eliminating formaldehyde is desired.